The contest is largely a three-horse race between a left-wing senator, a businessman and a right-wing lawmaker.
The election is held after months of public recrimination between current left-wing President Gustavo Petro and his US counterpart Donald Trump.
As Colombia prepares to elect a new president, candidates are debating the legacy of Gustavo Petro's signature policy.
Rights office says the violence could hinder 'exercise of political rights' ahead of May vote to replace Gustavo Petro.